As the photovoltaic industry plays an important role in clean energy gradually, manufacturers of solar cells are trying their best to improve production yield and reduce manufacturing cost at the same time. However, several defects such as crack, impurity, short circuit, low PCE etc. will be created in the solar cells during manufacturing process, which cannot be located easily by simple visual inspection. Thus it's an important and necessary process to detect and test the solar cells before they are assembled to be a solar cell panel.
For crystalline silicon (C-Si) solar cell panel, which is implemented by assembling multiple segmental solar cells in series connection, every small segment of the solar cells will be inspected and classified as different grades according to their performances before they are assembled. Commonly, conventional crack and short circuit detection of the solar cell includes photoluminescence (PL) detection and electroluminescence (EL) detection. PL detection is carried out by collecting fluorescent signals of the solar cell and applying charge-coupled device (CCD) imaging according to photoluminescence principle, then the detects such as crack, impurity, short circuit etc. will be detected by image analysis, and in turn, the quality and performance can be judged. For EL detection, it generates an electric field by applying voltage at two terminals of the solar cell, the electrons excited by the electric field impacts luminescence center thereby causing to illuminate, and then an infrared imaged of the solar cell will be captured by a CCD camera with high resolution, thereby detecting defects of the solar cell.
However, PL and EL detection in small scale is not practical for thin-film type solar cell panel such as CIGS, CdTe, a-Si solar cell panel which are normally fabricated in large panel format. Without inline inspection and defect checking, the uniformity and defect level for within these monolithically integrated solar panels can be different and various, which will impact the quality and performance of the solar cell panel and, in turn impact the final production yield.
Thus, it is desired to provide a testing method and a testing apparatus of solar cell panel to test the solar cell panel efficiently and detect defects accurately so that the defects can be corrected and fed back to improve manufacturing process.